The invention relates to a catalytic gas combustion device for an appliance for personal use, in particular a hair shaping appliance, such as a hair curler or hair dryer.
Catalytic gas combustion devices of this type are used in appliances for personal use which generate heat energy by means of gas without electrical current. An appliance of this type is sold, for example, by the applicant itself under the designation HS3 Plus as xe2x80x9cBraun Style Shaperxe2x80x9d. This hair shaping appliance includes a catalytic gas combustion device consisting of a piezoelectric igniter with two ignition electrodes arranged next to one another. These ignition electrodes are arranged in the chamber surrounding the catalyst.
To operate the appliance, the gas supply initially is opened mechanically via a valve device on the gas supply device. Gas flows through the gas supply device, mixing with air, and then passes into the catalyst space. The catalyst includes a tubular screen part, and the gas/air mixture also passes into the chamber, where it is flows around the ignition electrodes. The piezoelectric igniter is then ignited by hand, and sparks jump from one electrode to the other, causing the gas/air mixture in the chamber to ignite and thus initiate catalytic combustion at the catalyst. A certain amount of time elapses before the gas/air mixture reaches the electrodes, and only then is it possible to ignite the gas/air mixture.
The object of the invention is to provide a catalytic gas combustion device for an appliance for domestic use, in particular a gas curler or hair dryer, in which the ignition of the gas/air mixture can be induced shortly after the opening of the gas supply, even simply by the initiation of the ignition operation, so that catalytic combustion commences quickly.
The invention relates to a catalytic gas combustion device including a bypass. The bypass allows part of the main gas stream to be branched off and supplied to the ignition electrode to cause the combustion of the gas by the actuation of the ignition device after a very short time. As a result, the gas located in the catalyst space and surrounding the catalyst bums abruptly and the catalyst thus reaches its operating temperature, which is necessary for satisfactory catalytic combustion.
The ignition device may be of any desired type, for example, a piezoelectric ignition device, an electric ignition device formed by an incandescent filament or a purely mechanical ignition device. The ignition system operates reliably, since, owing to the short path the gas travels and the rapid flow of the gas around the igniter, the ignition operation can be reproduced and ignition failures avoided. xe2x80x9cGas supplyxe2x80x9d means those components of the gas combustion device which are connected to the gas valve for controlling the gas flow. Part of the catalyst may be provided in the bypass.
In some preferred embodiments, the gas supply includes a first gas-permeable cover downstream of the bypass. The gas-permeable cover may act in a similar way to a throttle valve, so that a defined quantity of the gas arrives at the ignition device reliably and quickly via the bypass. The higher the gas permeability of the first cover, the more gas is supplied to the chamber of the catalyst and the less gas arrives at the ignition device.
The outlet of the bypass may also include a second gas-permeable cover having a permeability selected in coordination with the first cover, to provide sufficient gas to the ignition device via the bypass. This second cover also has the advantage that the gas explosion advancing from the ignition device does not pass into the chamber of the catalyst via the bypass, but arrives at the catalyst only from outside via the space surrounding the catalyst.
The first and the second covers may consist of a metallic screen, the passages of which pass through a sufficient quantity of the gas both to the catalyst and to the ignition device. The metallic screen of the second cover also may serve as a kind of gas throughflow limiter, so as not to allow too much gas to arrive at the ignition device. The two covers may also serve to improve the mixing of the gas when it flows through the covers.
In some embodiments including the first gas-permeable cover, the gas supply includes a tubular housing for conducting the gas. The tubular housing includes an outlet, and the catalyst includes a bowl-shaped screen body with an inlet connected to the outlet. The first gas-permeable cover is positioned at a transition from the outlet to the inlet. This arrangement results in a particularly simple production of the gas supply device connected to the catalyst and to the cover, since the gas supply device can be produced easily and can be mounted in a simple way.
In some embodiments including the tubular housing, the bypass comprises a slot at the end of the tube including the outlet. The slot is covered by the second cover. This arrangement also allows a simple production of the bypass at the gas supply device, in that a slot is formed laterally at the bore and is delimited at its orifice by the second cover.
In other embodiments including the tubular body, the first cover and the second cover comprise a single covering part. The first cover includes an element having an essentially bowl-shaped cross section, with an adjoining annular flange, and the second cover includes a tab angled on the flange. The production, stock-keeping of parts and assembly of the appliance are simplified considerably owing to the one-part design of the first and second cover as a covering part. This lowers the costs of the appliance.
In some embodiments including the single covering part, the bowl-shaped element is centered in the inlet. The covering part is positioned on the gas supply device in such a way that, at the same time, the tab covers at least part of the slot from the outside. This permits a simple connection of the catalyst to the cover and the gas supply device, in that the cover is centered on the gas supply device and the catalyst is in turn centered on the cover. The catalyst can thereby be connected firmly to the gas supply device, for example via a screw connection, adhesive bonding, plastic deformation or otherwise a generally known fastening device.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.